Abstract TextureView/BufferDelegate locking into LockableSharedPtr

An atomic transactional loop was performed on the backing `std::shared_ptr` inside `BufferView`/`TextureView`'s `lock`/`LockWithTag`/`try_lock` functions, these locks utilized `std::atomic_load` for atomically loading the value from the `shared_ptr` recursively till it was the same value pre/post-locking. 

This commit abstracts the locking functionality of `TextureView`/`BufferDelegate` into `LockableSharedPtr` to avoid code duplication and removes the usage of `std::atomic_load` in either case as it is not necessary due to the implicit memory barrier provided by locking a mutex.

app/src/main/cpp/skyline/gpu/buffer_manager.cpp

@@ -86,7 +86,7 @@ namespace skyline::gpu {
 
             // Transfer all delegates references from the overlapping buffer to the new buffer
             for (auto &delegate : overlap->delegates) {
-                atomic_exchange(&delegate->buffer, newBuffer);
+                delegate->buffer = newBuffer;
                 if (delegate->usageCallback)
                     delegate->usageCallback(*delegate->view, newBuffer);
             }